The objectives are to study the development of sustained, endogenous attention in young infants, and to relate developmental trends in sustained attention to concurrent heart rate (HR) changes. The specific aims are: 1) To study sustained, subject-controlled attention in infants from 8 to 26 weeks of age, and to study the control of saccadic and smooth pursuit eye movements during heart-rate-defined attention phases, in order to infer the neuro-developmental systems controlling attention-directed eye movements during attention; 2) To expand the study of sustained, subject-controlled attention in infants to the study of infant recognition memory, television watching, and object examination and toy play. This research is important in determining the patterns of attention found in normal children, relating those attention patterns to physiological processes (HR, EEG), and may provide a "model preparation" for the study of children with irregular patterns of attention. The proposed experiments will study infants primarily in the first year of life, but one experiment will extend the study of heart-rate-defined attention phases to 1 and 2 year old children. Experiment 1 will examine the characteristics of eye movements during peripheral stimulus localization at the early parts of this age range (8, 11, 14 weeks), and will also study infants younger than this age range (5 weeks). Experiment 2 will examine covert shifts of attention in infants from 2 to 6 months of age to peripheral stimuli and will introduce the use of EEG/ERP (event-related- potentials) to the study of infant sustained attention. In Experiment 3, the effect of sustained attention on the ERP response to novel and repeated stimuli' will be studied in infants ranging in age from 4.5 to 9 months. Experiment 4 will extend the study of sustained attention to infants watching television (Experiment 4). This experiment will extend the age range of the study of HR-defined attention phases to older infants and the early preschool years (6 months to 2 years). It is predicted that 1) sustained attention will show age differences, whereas other attention phases do not; 2) eye movement characteristics and ERP responses to peripheral stimuli will be significantly affected by attention status; 3) sustained attention, and the MR-defined attention phases, will be closely related to recognition memory, and television viewing in older infants and children in the early preschool years (up to age 2 years).